There are some constituents of the starting materials used in the production of beverages, which can detrimentally affect the implementation of the production process or the quality of the end product. For example when opening beer bottles, so-called gushing frequently occurs.
The term gushing is used to denote an uncontrolled and abrupt escape of foam and beer when opening a beer bottle, which is not caused by high temperatures or shaking. That phenomenon occurs again and again in entire beer batches and is extremely unpleasant for the consumer. Various factors are discussed as being the causes of gushing.
Triggers of so-called primary gushing are hydrophobins and further fungal metabolites (polar lipids, proteolytic decomposition products of lipotransfer proteins (LPT)), which are deposited at phase interfaces and modify the interface energy thereof, which has an effect on the growth of crystals from aqueous solution.
Hydrophobins are small surface-active amphiphilic proteins (about 100 amino acids) which are deposited in particular from filamentous fungi of the genus Fusarium and which pass into the beer by way of grain infected with those fungi. They spontaneously aggregate to form very stable, monomolecular membranes and have a tendency to micellization.
Secondary or technological gushing is caused by calcium oxalate precipitations caused by the process engineering involved and metal ions like for example Fe3+. It will be noted however that rinsing agent residues as well as rough surfaces of the containers or bottles are sometimes found to be the causes of gushing.
Oxalic acid is present in the malt in high levels of concentration. In the wort oxalic acid is in the range of <60 mg/l, while in the beer it is still present in the region of <25 mg/l. If that oxalic acid precipitates in the form of calcium oxalates many crystal crystallization seeds are formed for gas bubble formation. The greater the number of particles, the correspondingly higher is the gas bubble formation potential.
Over half of the breweries have already once had problems with the gushing phenomenon. In that respect all five high-turnover main kinds of beer like Pils, lager, Export and wheat beer have been affected. As gushing not only results in a loss of image in respect of breweries, but all malt houses are also indirectly affected thereby, both the brewery industry and also the malt industry are highly interested in methods of and processes for avoiding gushing.
Hitherto there has not been a guaranteed method which could adequately prevent gushing. In spite of recent knowledge regarding the cause of gushing it has hitherto not been possible to control the occurrence thereof in the industry.
Admittedly hops are known for their slightly gushing-suppressing effect so that in part the attempt was made to reduce the problem by the addition of isomerized hop oils to the brewing process. A disadvantage of that approach however is that the beer aroma is markedly influenced by the increase in the proportion of hops. In Germany an increase in the proportion of hops is also not allowed because of the purity requirement.
As the occurrence of hydrophobins is very greatly weather-dependent, some barley and thus malt years are affected more greatly than others. Frequently therefore various malt batches are blended to minimize at least primary gushing. That however means that the malt houses are involved in an increased storage implementation if different malt batches from different years with a differing gushing potential are to be blended. In addition at the present time there is not a reliable convincing test method for determining the gushing potential of malt.
CO2 release at calcium oxalate precipitations is often counteracted by meteredly adding soluble calcium salts (CaSO4, CaCl2) in the mashing-in operation by way of the brewing water. Difficultly soluble calcium oxalate is then precipitated during the cold storage phase of the green beer, and can then be removed in specifically targeted fashion with the sedimented yeast or in the filtration process. That method however entails the disadvantage that the calcium salts must be very highly metered (CaSO4:Ca oxalate in the ratio>5:1). The total salt content of the later beer is markedly altered thereby. In addition CaCl2 and CaSO4 markedly influence the flavor of the beer. CaCl2 can also lead to chloride corrosion effects in relation to high-quality steel.
Particularly promoted by the fact that the added calcium salt reduces the pH value, which increases the solubility of calcium oxalate and thus counteracts complete precipitation of calcium oxalate, there is in addition the danger that the non-precipitated Ca2+ ions and oxalic acid are dragged over the filters. That can entail further precipitation of calcium oxalate after filtration, which can lead to unwanted clouding of the beer or can trigger gushing after having been filled into bottles. That effect can be increased in particular by additional calcium absorption from the kieselguhr of the filter.
To sum up it can be established: hitherto there is not a reliable and secure method of preventing gushing. The existing methods require an additional method step or markedly affect the aroma profile of the beer product.
In relation also to other beverages such as for example in wine production or in the production of fruit juices, the starting materials used in the production of those beverages involve constituents which can detrimentally influence the implementation of the production process or the quality of the end product, like for example high tartaric acid contents in the must or high contents of other fruit acids in the juice of different kinds of fruit.